The present invention relates to the field of electric motors and comprises an energy conserving electrical apparatus designed to utilize otherwise wasted electromagnetic energy associated with back emf in motor windings, and also is designed to recover a further portion of unused electromagnetic energy induced in motor windings during normal motor operation, thereby conserving electrical energy and increasing motor efficiency.
During the operation of a conventional AC or DC electric motor, a plurality of stationary magnetic poles spaced about the rotor or armature are alternately energized to magnetically attract and repel the magnetic poles of the rotor to achieve rotor rotation. Typically, a pair of stationary poles is energized as the rotor poles approach the pair in order to attract the rotor. Polarity of the stationary poles is then reversed as the rotor poles pass the stationary poles in order to repel the rotor poles. During the brief time interval in which the rotor's poles directly confront the stationary field poles, the rotor poles are neither attracted nor repelled because of the distribution of force vectors between rotor poles and stationary poles. Accordingly, during this brief time interval there is little advantage to energizing the field windings. As the rotor poles pass the stationary poles the magnetic field of the rotor induces a current increment in the field windings of the stationary poles. This induced current and its well known, associated back emf serves no useful purpose in the motor and normally opposes current flow in the field windings. In addition, such induced current produces unwanted heat in the motor. It would be desirable to utilize these induced increments of current for a useful purpose, and the present invention accomplishes this object.
In conventional motors a second loss of energy occurs as a result of Lenz's law. Each time that current to a field winding of the motor is turned off, a reverse current is induced in the winding and with it an opposing field is generated in the winding which tends to oppose shrinkage of the original field. This reverse current associated with the opposing field has not been utilized for any constructive purpose in the past and the energy used to generate the opposing field has been wasted. The present invention utilizes this otherwise wasted energy and thus further conserves energy and increases motor efficiency.